The present invention relates to an optometry apparatus having an optical element by which targets can be seen as if they were dispersed in a plane orthogonal to an optical axis and presented simultaneously at a different distance or position in a direction of an optical axis through examined eyes to be subjected to optometry, and a diffraction grating plate as an optical element used in the same.
Conventionally, an optometry apparatus makes a precise decision of an astigmatic axis of examined eyes to be subjected to optometry and of an astigmatic degree by use of a cross cylinder lens. As a method for deciding the astigmatic axis and astigmatic degree precisely using this cross cylinder lens, a cross cylinder method and an auto-cross cylinder method are known.
In any method, firstly a spherical degree S, a cylindrical degree C, and an axial angle A of a cylindrical axis O are roughly measured, thereafter, the astigmatic axis of the examined eyes to be subjected to optometry and the astigmatic degree are precisely measured.
For example, it is assumed that a spherical degree S (=xe2x88x921.00D), a cylindrical degree C (=xe2x88x920.50D) and an axial angle A of a cylindrical axis O (=90 degree) are set as a result of the optical characteristic of one lens of eyeglasses in use currently by a lens meter.
At the time of optometry, first of all, in order to remove accommodation power of eyes, as shown in FIG. 1, a spherical lens 2 whose the spherical degree S is, for example, +3.00D, which is higher than a prospective degree, is set to an optometric window of a correction optical system 1 by fogging, and an eyesight-test chart is shown to a subject. In the case of the spherical degree S (=xe2x88x921.00D), the spherical lens 2 with the spherical degree S (=+2.00D) is set to the optometric window, and the spherical degree S of the spherical lens 2 to be set to the optometric window is reduced by xe2x88x920.25D so as to increase eyesight.
Then, an astigmatic test chart 3 illustrated in FIG. 2 is shown to the subject at the stage which is one step before desirable eyesight, and the subject is asked how the astigmatic test chart 3 is seen.
In a case where the astigmatic test chart 3 is blurredly seen uniformly, it can be judged that the subject is not a person with astigmatism. Here, it is assumed that the subject is a person with astigmatism. For example, if an answer xe2x80x9cI can see the direction at 3 o""clock clearlyxe2x80x9d is received in response to a question xe2x80x9cwhich direction at a clockwise can you see?xe2x80x9d, a cylindrical lens 4 is set to the optometric window of the correction optical system 1 and the cylindrical axis O is set in a direction orthogonal to a direction where clear vision can be obtained. Namely, the axial angle A of cylindrical axis O is set to 90 degrees.
After that, the cylindrical degree C of the cylindrical lens 4 to be set to the optometric window is increased 0.25 by 0.25, and the approximate measurement is completed when the degree of the cylindrical lens 4 reaches a value where the astigmatic test chart 3 is clearly seen uniformly.
Additionally, in FIG. 1, reference numeral O1 denotes an optical axis of the correction optical system 1.
Next, precise measurement of the cylindrical axis O and cylindrical degree C is performed.
In case of the cross cylinder method, a cross cylindrical lens 5 is inserted in the correction optical system 1. This cross cylinder lens 5 is structured such that the axis of (xe2x88x92) axial cylindrical lens is orthogonal to that of (+) axial cylindrical lens as shown in FIG. 1.
Then, an intermediate axis 6 of the cross cylindrical lens 5 is allowed to conform to the cylindrical axis O of the cylindrical lens 4. Next, the cross cylindrical lens 5 is reversed using the intermediate axis 6 of the cross cylindrical lens 5 as a central axis. Then, the subject is allowed to look at a point group chart 7 of FIG. 3.
Before and after the cross cylindrical lens 5 is reversed at the time of showing this point group chart 7, the cylindrical lens 4 and cross cylindrical lens 5 are integrally rotated in a direction where a clear view is obtained by, for example 5 degrees to measure the axial angle A of the cylindrical lens 4 precisely.
Sequentially, as illustrated in FIG. 4, any one of (+) axis and (xe2x88x92) axis of the cross cylindrical lens 5 is confirmed to the cylindrical axis O of the cylindrical lens 4. FIG. 4 shows a state in which (+) is confined to the cylindrical axis O. Then, the point group chart of FIG. 3 is shown to the subject. Next, the cross cylinder lens 5 is reversed using the intermediate axis 6 as a central axis and the (xe2x88x92) axis is conformed to the cylindrical axis O. Then, the point group chart of FIG. 3 is shown to the subject. After asking the subject a question about which way the chart can be clearly seen before or after the cross cylindrical lens 5 is reversed, the cylindrical degree C of the cylindrical lens 2 is set to a direction where a clear view can be obtained.
Thus, precise measurement of the subject""s astigmatic axis and astigmatic degree is completed.
In case of the auto-cross cylinder method, an auto cross cylindrical lens 8 shown in FIG. 5 is used. This auto cross cylindrical lens 8 includes a triangular prism 9 and cross cylindrical lenses 10, 11. The cross cylindrical lenses 10 and 11 have the degree of, for example, xc2x10.25D or xc2x10.5D, and plus and minus axes of the cross cylindrical lenses 10 and 11 are orthogonal with respect to each other.
The precise measurement of the astigmatic axis and astigmatic degree using this auto cross cylindrical lens 8 is carried out, for example, as follows:
The approximate measurement of the spherical degree S, cylindrical degree C, and axial angle A of cylindrical axis O is the same as the case of the cross cylinder method.
After the approximate measurement of the spherical degree S, cylindrical degree C, and axial angle A of cylindrical axis O, an intermediate axis 12 of the auto cross cylindrical lens 8 is conformed to the cylindrical axis O of the cylindrical lens 4 as shown in FIG. 6. Consequently, the plus axis (+) of the upper-side cross cylinder lens 10 is set to a direction at 45 degrees with respect to the cylindrical axis O and the minus axis (xe2x88x92) thereof is set to a direction at 135 degrees. Moreover, the minus axis (xe2x88x92) of the lower-side cross cylinder lens 11 is set to a direction at 45 degrees with respect to the cylindrical axis O and the plus (+) thereof is set to a direction at 135 degrees.
Then, the point group chart 7 of FIG. 3 is similarly shown to the subject so that the subject is allowed to perform comparison between the point group chart 7 seen through the upper-side cross cylinder lens 10 and the point group chart 7 seen through the lower-side cross cylinder lens 11 simultaneously to check which chart can be clearly seen. Then, the cylindrical lens 4 is rotated integrally with the auto cross cylinder 8 in the direction where a good view can be obtained. Thus, the axial angle A of the cylindrical axis O is decided.
After that, the cross cylinder lenses 10 and 11 are rotated so that the plus axis (+) of the cross cylinder lens 10 is conformed to the cylindrical axis O and the minus (xe2x88x92) of the cross cylinder lens 11 is conformed to the cylindrical axis O as illustrated in FIG. 7. After performing comparison between the point group chart 7 seen through the cross cylinder lens 10 and the point group chart 7 seen through the cross cylinder lens 11 simultaneously to check which chart can be clearly seen, the cylindrical degree C of the cylindrical lens 4, which is inserted in the optical path of the correction optical system 1, is changed to the direction where the good view can be obtained.
Thus, precise measurement of the axial angle A of the cylindrical axis and cylindrical degree C is completed.
Next, precise measurement of the spherical degree S is performed.
In this precise measurement of the spherical degree S, a so-called red and green chart 13 is shown as illustrated in FIG. 8. In a case where a target seen through a red filter can be seen well, since such a situation is considered that correction is lack, the spherical degree S of the spherical lens 2 is increased. In a case where a target seen through a green filter can be seen well, since such a situation is considered that correction is excessive, the spherical degree S of the spherical lens 2 is decreased.
Thus, the precise measurement of the spherical degree S is completed.
However, in the optometry apparatus by the cross cylinder method, since an operation to reverse the cross cylinder lens 5 is carried out at the target comparing time, the targets cannot be compared simultaneously. Accordingly, since judgment is made by separated observation in which judgment is made with a time difference, it is difficult for the subject to judge which the target can be seen well.
Moreover, there is a disadvantage in which the spherical degree S, cylindrical degree C and the axial angle A of the cylindrical axis cannot be measured simultaneously,
Still moreover, many subjects answer that the subject can see the respective points 7a more easily whose profile lines 7b are clearly seen in the direction of astigmatic axis as illustrated in a partially enlarged view of FIG. 9, as compared with the respective points 7a of the point group chart 7 of FIG. 3 which are blurredly seen uniformly.
On the other hand, in the optometry apparatus by the auto cross cylinder method, since a contrastive observation that performs comparison between the targets simultaneously is performed, the subject can easily judge which the target can be seen well as compared with the case of using the cross cylinder method.
However, similarly to the cross cylinder method, this auto cross cylinder method has a disadvantage in which the spherical degree S, cylindrical degree C and axial angle A of cylindrical axis cannot be measured simultaneously. Moreover, similar to the cross cylinder method, many subjects answer that the subject can see more easily the respective points 7a whose profile lines 7b are clearly seen in the direction of astigmatic axis as illustrated in a partially enlarged view of FIG. 9, as compared with the respective points 7a of point group chart 7 of FIG. 3 which are blurredly seen uniformly.
Still moreover, though the contrastive observation that contrasts the targets simultaneously and compares them can be carried out, the number of targets to be compared is only two and it is difficult to judge which is clearly seen.
In addition, in a case where the subject is extremely farsighted or nearsighted, a difference occurs in the way to see the targets simultaneously presented due to influence of aberration of the correction optical system 1 unless the eyes to be subjected to optometry are set to a correct position.
In the case of precise measurement of spherical degree using the red and green test chart 13, there are many answers indicating that the target with a favorite color is seen well.
The present invention has been made with consideration given to the aforementioned problems, and it is an object of the present invention is to provide an optometry apparatus that can measure a spherical degree S, a cylindrical degree C and an axial angle A of a cylindrical axis O at one time, so that targets are seen as if they were disposed in a plane orthogonal to an optical axis and shown simultaneously at a different distance or position in a direction of the optical axis.
An optometry apparatus according to the present invention comprises an optical element constructed so that targets appear to examined eyes to be subjected to optometry as if the targets were dispersed on a plane orthogonal to an optical axis and shown simultaneously at a different distance or position in a direction of the optical axis.
In an optometry apparatus according to the present invention, the optical element is formed of a diffraction grating plate where periodicity of a diffraction grating changes.
An optometry apparatus according to the present invention comprises an optical element in a correction optical system which has a spherical lens and a cylindrical lens and corrects eyes to be subjected to optometry, the optical element being constructed such that targets appears to the eyes as if the targets were dispersed in a plane orthogonal to an optical axis and shown simultaneously at a different distance or position in a direction of the optical axis.
In the optometry apparatus according to the present invention, the optical element is capable of going/coming to/from an optical path of the correction optical system.
In the optometry apparatus according to the present invention, then optical element is formed of a diffraction grating plate where periodicity of a diffraction grating changes.
In the optometry apparatus according to the present invention, when the diffraction grating plate is inserted in an optical axis of the correction optical system, the targets are shown by a single-color light source.
In the optometry apparatus according to the present invention, when the diffraction grating plate is inserted in the optical axis of said correction optical system, a light quantity of the single-color light source is increased.
In the optometry apparatus according to the present invention, a subject himself/herself designates a target, which seems to be the best among the plurality of targets shown simultaneously and adjusts said correction optical system.
In the optometry apparatus according to the present invention, matrix signs, which can designate the plurality of targets in the form of matrix, are simultaneously shown to the eyes to be subjected to optometry such that the subject himself/herself is caused to designate the target, which seems to be the best among the plurality of targets shown simultaneously.
In the optometry apparatus according to the present invention, the matrix signs are shown in an optical path of the correction optical system through a half mirror.
In the optometry apparatus according to the present invention, the matrix signs are shown with a wavelength by which no diffraction power is generated.
In the optometry apparatus according to the present invention, the subject himself/herself adjusts the correction optical system using a joystick such an target, which seems to be the best among the plurality of targets shown simultaneously, is positioned on an optical axis of the correction optical system.
In the optometry apparatus according to the present invention, the diffraction grating plate is rotated together with the cylindrical lens, so that a spherical degree, a cylindrical degree and an axial angle of a cylindrical axis are precisely measured.
In the optometry apparatus according to the present invention, the diffraction grating plate is rotated by 45 degrees from an initial setting state to determines a spherical degree, a cylindrical degree and an axial angle of a cylindrical axis by calculation. A spherical degree, a cylindrical degree and an axial angle of a cylindrical are determined by calculation where the spherical degree, the cylindrical degree and the axial angle of cylindrical axis determined by the calculation are synthesized with a cylindrical degree and an axial angle of a cylindrical axis determined by approximate measurement. The spherical degree, the cylindrical degree and the axial angle of cylindrical axis are precisely measured by the synthesized spherical degree, cylindrical degree, and axial angle of cylindrical axis obtained by this calculation.
In the optometry apparatus according to the present invention, the diffraction grating plate is rotated by 60 degrees two times from an initial setting state to determine a spherical degree, a cylindrical degree and an axial angle of a cylindrical by calculation. A spherical degree, a cylindrical degree and an axial angle of a cylindrical axis are determined by calculation where the spherical degree, the cylindrical degree and the axial angle of cylindrical determined by the calculation are synthesized with a spherical degree, a cylindrical degree and an axial angle of a cylindrical axis determined by approximate measurement. The spherical degree, the cylindrical degree and the axial angle of cylindrical axis are precisely measured by the synthesized spherical degree, cylindrical degree, and axial angle of cylindrical axis determined by this calculation.
A diffraction grating plate according to the present invention constructed such that targets appear to eyes to be as if the targets were dispersed in a plane orthogonal to an optical axis and shown simultaneously at a different distance or position in a direction of an optical axis through eyes to be subjected to optometry.